In certain types of medical procedures which involve the insertion of catheters into the body, it is often necessary that the location of the catheter be precisely known. The location of the catheter is usually accomplished by means of radiographic observation. In order to employ radiographic means to determine the position of the catheter in the body, such as in a body cavity or in a vein or artery, the catheter must be at least partially opaque to x-rays. However, optimally, the catheter must not only be at least partially opaque to x-rays, but should also be flexible, strong, transparent to visible light, non-toxic, biologically compatible, stable upon contact with biological fluids, tissues, or drugs which are to be administered intravenously or otherwise, and should be able to withstand cleaning and sterilization procedures.
In the prior art, a number of different approaches have been used to render catheters opaque to x-rays. These have included applying a radiographically opaque substance onto the outer surface of the catheter and incorporating an x-ray opaque material within the catheter to thereby render the entire catheter radiographically opaque, as for example in U.S. Pat. No. 3,749,134. The approach of applying x-ray opaque markings to the outer surface of the catheter includes an extra step in the production of the catheter, which adds to the expense of the production of the catheter and to the catheter itself. Furthermore, these external markings are after destroyed or rendered relatively ineffective through cleaning or sterilization of the catheter. The approach of incorporating a radiographically opaque material into the catheter suffers from the drawback that these materials oftentimes render the catheter not only radiographically opaque, but also opaque to visible light. In the cases wherein these materials do not render the catheter optically opaque, there is present the disadvantage of having to incorporate an additional additive to the catheter material.
The present invention provides tubing which overcomes these disadvantages of the prior art and which meets all of the criteria necessary for a successful catheter for use in the medical and biological fields.